Spanish prosecutors have alleged that the four-time Ballon d'Or winner owes €14.8m (£12.9m) in unpaid taxes between 2011 and 2014.
They have accused the 32-year-old of using a shell company in the Virgin Islands to "hide" €28.4m (£25m) of income earned from image rights.
Ronaldo's agents GestiFute denied the allegations in a statement, which read: "There is no offshore structure for evading taxes. [Ronaldo has never] had a tax problem, contrary to what the Spanish prosecutors insinuate. All contractual modifications have been made to guarantee that the incomes [Ronaldo obtains] fully observe Spanish tax regulations."
The footballer's club have now responded, writing on their official website: "Cristiano Ronaldo has always shown since his arrival at Real Madrid CF, in July 2009, a clear will to fulfill all his tax obligations. Real Madrid CF is absolutely convinced that our player will prove his total innocence in this process."
Spanish prosecutors have claimed that Ronaldo declared €11.5m of earnings between 2011 and 2014 but actually pocketed €31.5m more.